Published online: 2019-11-13 Letters to the Editor not created a crater. The bone flap was replaced back. Dreaded complications In the immediate postoperative period the patient was noticed to have right hemiplegia of grade 2/5. of mistaken Computed tomography of brain showed persistence of subdural hypodensity with small hyperdense collection identity – Hygroma at the posterior margin, squashing of lateral ventricles, midline shift and mass effect [Figure 1b]. The patient vs effusion following was immediately taken for removal of bone flap, and evacuation of the loculated fluid. Following the removal decompressive of the bone flap, on attempted durotomy, we observed craniotomy that the dura was abnormally thickened [Figure 1c] and measured approximately half‑a‑centimeter thick. There was a thin, dirty grey membrane covering the brain Sir, surface containing xanthochromic fluid. The membrane The first principle of ethical medical practice is primum was excised, xanthochromic fluid evacuated and a non nocera (first, do no harm). However, ignorance lax duroplasty performed using fascia lata graft. The may sometimes lead to such complications, which histopathological examination of the material showed could be avoided. Development of subdural hygroma fragments of granulation tissue comprising multiple following a decompressive craniectomy though proliferating blood vessels lined by endothelial cells, described in literature is infrequently concentrated fibroblastic proliferation, extravasated red blood cells upon. Development of hygroma is usually considered and mild inflammatory infiltrate and the membrane was benign, usually resolving following the replacement of diagnosed as chronic subdural membrane. The patient the bone flap due to restoration of normal cerebrospinal had a tormentous post‑operative period with infection fluid flow dynamics. A radiological mimic of this of the scalp flap. He started showing some improvement hygroma is effusion, with an incidence of upto 33%, in his limb power after 2‑weeks time and at discharge has unfortunately not received much attention in the after 4 weeks was able to walk with a spastic hemiplegic contemporary literature. We, herein, describe our gait, without support. He had a power of 4/5 in the inexperience in recognizing this entity in a 30 year male upper limbs, distal worser than proximal, requiring patient, who following a decompressive craniectomy help for feeding. came back for replacement of bone flap, had swelling of the scalp flap which on computed tomographic Subdural hygromas akin to hematomas are collections scans showed hypodense collection beneath the in the subdural space but contain cerebrospinal fluid meningo‑galeal complex, which was misdiagnosed as as opposed to blood clots of various ages.[1‑4] Head hygroma. The tormentous postoperative period and injuries, post‑decompressive craniotomy, brain atrophy, morbidity the patient suffered is described in for others spinal drainage are few causes of formation of subdural to learn from our mistake. hygroma.[5] Various theories have been described trying to eludicate the natural history of what was proposed A 30‑year‑male patient who had undergone right by Feng et al.,[6] as two ends of the same spectrum. fronto‑temporo‑parietal decompressive craniectomy Arachnoid though tightly attached to pial surface by for traumatic right fronto‑temporo‑parietal acute trabeculae is separated by the cushion of cerebrospinal subdural hematoma with parietal contusion and mass fluid. Arachnoid barrier cell layer is separated from effect and midline shift, operated in 2008, presented the dura with an interface layer. The meningeal and for replacement of bone flap in 2012. At the time periosteal dural layers are tightly bound by collagen of discharge the patient was having a sensorium whereas the innermost dural border cell layer is of E4M6V5. The patient presented with the same devoid of collagenous architecture. Any insult to dural sensorium for bone flap replacement. CT scan of arachnoid interface, results in formation of potential the brain showed hypodense collection beneath the space with subsequent formation of subdural hygroma. meningo‑galeal complex, which was diagnosed as Added to this the loss of blood brain barrier following subdural hygroma [Figure 1a]. A lumbar drain was trauma leads to increased vascular permeability and placed in the immediate preoperative period. The flap hence oncotic pressure in the subdural space thus had sunken to the level with the adjacent skull but had starting a vicious cycle.[7‑9] Arachnoidal injury leads Journal of Neurosciences in Rural Practice | July ‑ September 2014 | Vol 5 | Issue 3 305 Letters to the Editor a b c Figure 1: (a) CT scan of brain showing the post-decompressive status with hypodense collection beneath the meningo-galeal complex with no evidence of mass effect. (b) Post‑bone flap replacement CT scan showing mild extradural hyperdense collection, with hypodense subdural collection with midline shift and mass effect. (c) Intraoperative picture showing thickened dural membrane (arrow) to leakage of cerebrospinal fluid with a ball‑valve caution has to be exercised, to monitor features of raised effect. The fluid so collected, remains unabsorbed and intracranial pressure. In case of raised intracranial thus the vicious cycle and fluid stagnation. Subdural pressure, the collection has to be drained off, either hygromas with gradual detachment from circulation pre‑ or intraoperatively.[12] leads to increase in protein content, triggering of inflammatory response, neomembrane formation with A repeat imaging study to know the change in the fragile capillaries. subdural collection, before replacement of bone flap might be useful. Altered cerebrospinal fluid dynamics and post decompressive craniectomy sequel can be prevented by Omekareswar Rambarki, Alugolu Rajesh augmented duraplasty which may restore cerebrospinal fluid dynamics and prevent the formation of subdural Department of Neurosurgery, Nizam’s Institute of Medical Sciences, Punjagutta, Hyderabad, India hygroma.[5] Address for correspondence: On computed tomography, hygromas are hypodense Dr. A. Rajesh, Department of Neurosurgery, Nizam’s Institute of Medical Sciences, whereas subdural hematomas vary from hypo to Punjagutta, Hyderabad - 500 082, India. hyperdense depending upon their chronological E-mail: [email protected] age (hyperacute‑ isodense; acute‑ hyperdense due to clot retraction; subacute‑ iso to hypodense due to References degradation of proteins in the clot; chronic‑ hypodense [10] 1. Schachenmayr W, Friede RL. The origin of subdural neomembranes. due to liquefaction of clot). Signal intensities I. Fine structure of the dura-arachnoid interface in man. Am J Pathol in Magnetic resonance imaging for hygromas are 1978;92:53-68. identical to CSF in all pulse sequences whereas they 2. Haines DE. On the question of a subdural space. Anatomical Record vary in intensities in subdural hematomas depending 1991;230:21. 3. Haines DE, Harkey HL, Al-Mefty O. The ‘subdural’ space: A new look at upon the age and pulse sequences (hyperactue an outdated concept. Neurosurgery 1993;32:111-20. stage: T1‑ iso, T2‑hyper; acute stage: T1‑iso, 4. Orlin JR, Osen KK, Hovig T. Subdural compartment in pig: T2‑ hypo; subacute: T1 and T2‑ hyper; chronic‑ T1 A morphologic study with blood and horseradish peroxidase infused [11] subdurally. Anat Rec 1991;230:22-37. and T2‑ hypo). Diffusion‑weighted images will, 5. Yang XF, Wen L, Shen F, Li G, Lou R, Liu WG, et al. Surgical however, show restricted diffusion in cases of subdural complications secondary to decompressive craniectomy in patients with hematoma. However, to obtain MR imaging requires a head injury: A series of 108 consecutive cases. Acta Neurochir (Wien) a strong suspicion. The protein content in hygromas 2008;150:1241-7. 6. Feng JF, Jiang JY, Bao YH, Liang YM, Pan YH. Traumatic subdural is identical to that of CSF whereas effusions have effusion evolves into chronic subdural hematoma: Two stages of the high protein contents with relatively normal sugar same inflammatory reaction? Med Hypotheses 2008;70:1147‑9. levels, thus differentiating them from fluid collections 7. Lee KS. The pathogenesis and clinical significance of traumatic subdural [12] hygroma. Brain Inj 1998;12:595-603. secondary to infections. 8. Jeon SW, Choi JH, Jang TW, Moon SM, Hwang HS, Jeong JH. Risk factors associated with subdural hygroma after decompressivecraniectomy Hygromas are rarely symptomatic and most of them in patients with traumatic brain injury: A comparative study. J Korean resolve spontaneously. However, symptomatic cases Neurosurg Soc 2011;49:355-8. 9. Aarabi B, Chesler D, Maulucci C, Blacklock T, Alexander M. Dynamics of require surgical intervention wherein replacement subdural hygroma following decompressive craniectomy: A comparative of bone flap is considered the best option. However, study. Neurosurg Focus 2009;26:E8. 306 Journal of Neurosciences in Rural Practice | July ‑ September 2014 | Vol 5 | Issue 3 Letters to the Editor 10. Lee KS, Bae WK, Bae HG, Yun IG. The fate of traumatic subdural Study has shown that in those cases of cerebral atrophy, hygroma in serial computed tomographic scans. J Korean Med Sci 2000;15:560-8. cortical veins and their branches traversing had 11. Fobben ES, Grossman RI, Atlas SW, Hackney DB, Goldberg HI, widened cerebrospinal fluid spaces over the cerebral Zimmerman RA, et al. Characteristics of subdural hematomas and convexities and these visualization of